Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
D2346-21 – Standard Test Method Technical Guide
This article discusses the technical requirements and procedures for ASTM D2346-21, the Standard Test Method for the determination of apparent density in leather specimens. This method is essential for evaluating loading and compression characteristics in finished leather goods.
📐 Specimen Geometry and Conditioning Requirements
The test specimen required for ASTM D2346-21 is a circular disk of conditioned leather. The specific geometry is defined by the cutting die dimensions.
| 🟦 Parameter | 📏 Specification | 🎯 Tolerance / Notes |
|---|---|---|
| Specimen Shape | Circular Disk | Cut from conditioned leather sample |
| Cutting Die Diameter | 2.7 in. to 3.0 in. | 68.6 mm to 76.2 mm |
| Conditioning Requirement | Per Practice D1610 | Standard atmosphere for leather testing |
⚠️ Scope Limitation: This test method specifically does not apply to the testing of wet blue or wet white leather. Alternative test methods must be used for those materials.
⚙️ Test Procedure and Calculation Methodology
The procedure involves three precise measurements: mass, thickness, and area. The thickness measurement must be averaged from readings taken in four distinct quadrants of the disk.
| 📐 Measurement | ⚡ Instrument / Method | 📊 Precision Requirement |
|---|---|---|
| Mass (Weight) | Analytical Balance | Nearest 0.001 g |
| Thickness | Gauge per D1813 (4 quadrants) | Nearest 0.025 cm (10 mil) per reading |
| Area | Test Method D2347 | Nearest second decimal place (cm²) |
The apparent density is calculated using the average thickness value obtained from the four quadrant readings. The precise formula is:
Apparent Density (g/cm³) = Weight of Specimen (g) / [Area (cm²) × Average Thickness (cm)]
The result must be reported to the second decimal place. The specimen tested may be the same disk used in Test Method D2347 for area measurement.
⚠️ Material Softness Limitation: This test method is unsuitable for very soft leathers such as chamois, whose thickness cannot be accurately measured by the standard thickness gauge referenced in D1813.
📊 Key Measured Properties and Significance
The primary property measured is the Apparent Density. By measuring this value, manufacturers and quality control laboratories can quantitatively evaluate the degree of loading or compression the leather has undergone during processing. This metric is crucial for determining the material’s suitability for specific applications, particularly in the footwear industry where density affects durability, flexibility, and performance.
❓ Frequently Asked Questions
🔍 Can this test method be applied to wet blue or wet white leather?
No. Section 1.1 of ASTM D2346-21 explicitly states that this test method does not apply to wet blue or wet white substrates.
💡 What is the primary significance of performing this apparent density test?
Based on Section 4.1, the test method is designed to evaluate the degree of loading or compression of leather, which are key indicators of material quality and processing history.
⚡ How must the thickness of the specimen be measured?
According to Section 7.2, the thickness must be measured in four quadrants of the disk, equidistant from the rim and the center, using a gauge described in Test Method D1813. Each measurement must be taken to the nearest 0.025 cm (10 mil).
📌 Is the apparent density value calculated in inch-pound or SI units?
While the die dimensions are specified in inch-pound units as standard, the calculation itself yields a metric result in g/cm³. The weight must be in grams, the area in square centimeters, and the average thickness in centimeters.